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DOI: 10.1002/ijch.201800155
Solvent Directed Synthesis of Molecular Cage and Metal
Organic Framework of Copper(II) Paddlewheel Cluster
[a]
[a]
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Abstract: A solvothermal reaction of a clip-type dicarboxylic change in the solvent from DMF to DMA [dimethylaceta-
acid H DCA [3,3’-((5-nitroisophthaloyl)bis(azanediyl))-diben- mide] the interlinking among the polyhedra was successfully
2
zoic acid] and Cu(NO ) in equimolar ratio in dimethylforma- terminated to get single crystals of a discrete coordination
3
2
mide (DMF) yielded MOF(CuCG1) which was formed by cage with DMA bound to axial position of Cu(II) (CuCG2).
interlinking [4+2] self-assembled polyhedral cages via coor- Similar termination of the interlinking was also achieved by a
dination between amide moiety present in the linker and the fast crystallization process to get discrete architecture
axial position of copper paddlewheel Cu (CO ) . Upon a CuCG1.
2
2 4
Keywords: copper(II) · self-assembly · cage compounds · crystal structure · MOF
1. Introduction
observed. Surprisingly, this produced only a discrete architec-
ture and no interlinking among the polyhedra was observed.
Metal-ligand coordination has emerged as an exciting tool to
design and synthesize molecular architectures of various
shapes and sizes constructed by from organic ligands and
metal ions with desired directionality. Self-assembly of such
organic/inorganic building blocks may produce either metal-
2. Result and Discussion
[1]
The ligand H DCA was synthesized following the modified
2
[2]
[14]
1
13
organic frameworks (polymeric)
or discrete molecular
reported procedure, and characterized by H NMR and C
NMR (Figures 1 and SI). All the peaks in the H NMR spectra
were successfully assigned with the help of Hꢀ H COSY
spectrum. The ligand was incorporated with functionality like
nitro and amide which would interact with the solvent
molecules through hydrogen-bonding, to improve the solubil-
[3]
1
polyhedron (single entity). Chemists mainly interest on these
materials due to the prospect of hosting guest molecules using
supramolecular interaction and carry out diverse applications
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1
[
4]
[5]
[6]
[7]
e.g. sensing, gas storage, separation, catalysis, proton
[
8]
[9]
conductivity, drug delivery and trapping transient metasta-
[
10]
ble state etc. Although, from a design perspective some of
the MOFs can be considered as an assembly of discrete
molecular polyhedron, very few examples are reported in the
ity of the desired molecular architecture. The ligand H DCA
2
attains different conformations which would produce various
donor angles, however DFT calculation suggests the presence
of two possible conformers 1 and 2 respectively having an
almost 08 donor angle (Scheme 1). Moreover, the conformer 1
is energetically more favoured having a planar configuration
which would be preferred during the self-assembly process;
whereas, the paddlewheel Cu (CO ) cluster having a 908 bite
[
11]
literature.
Stepwise assembly of MOFs by interlinking
discrete polyhedra imposes difficulty as the intermediate
interlinked polyhedra are not always soluble.
have used molecular polyhedra designed from a dicarboxylic
[
12]
Zhou et al.
[
13]
acid and a copper(II) paddlewheel cluster and interlinked
them with pyridyl bridging ligands to access metal-organic
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2 4
angle can interact with this 08 conformer to produce a [2+4]
self-assembled molecular polyhedron.
[
11a]
framework.
However, introduction of such bridging ligands
may complicate the self-assembly process by interacting with
the molecular polyhedra to disrupt their original shape.
Herein, we report the design and synthesis of a unique
discrete molecular architecture CuCG1 from the self-assem-
bly of an amide-functionalized clip-type donor 3,3’-((5-nitro-
Therefore,
a
self-assembly
reaction
between
Cu(NO ) ·3H O and H DCA in an equimolar ratio was carried
3
2
2
2
out in DMF under solvothermal condition for 48 h at 1108C.
The resulting blueish solution indicates the formation of a
discrete molecular architecture CuCG1 which is soluble in
isophthaloyl)bis(azanediyl))-dibenzoic acid (H DCA) and a
2
Cu(II) paddlewheel Cu (CO ) cluster (Scheme 1) in DMF.
2
2 4
[
a] P. Howlader, P. S. Mukherjee
Interestingly, the pseudo donor unit (amide group) present into
Department of Inorganic and Physical Chemistry, Indian Institute of
Science, Bangalore, 560012
E-mail: psm@iisc.ac.in
H DCA interlinks these polyhedra to produce a 3D metal-
2
organic framework MOF(CuCG1). However, when the same
reaction was carried out in DMA (DMA=N,N-dimethylaceta-
mide), formation of similar discrete polyhedron CuCG2 was
Isr. J. Chem. 2019, 59, 1–8
© 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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ÞÞ
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